1. Field of the Invention
This invention relates to an improvement in mounting structure for flexible printed wiring boards, and more particularly to a mounting structure for a flexible printed wiring board, which is arranged to enable the portion of the printed wiring board protruding from the rear surface of a casing such as, for example, an instrument casing to be fixedly secured.
2. Description of the Prior Art
The mechanism of instruments for motorcars has become complicated increasingly of late, and such equipment has become deluxe in general, so that electrical circuits thereof have become extremely intricate.
Therefore, wirings leading to instruments for motorcars are made generally using printed wiring boards. In particular, flexible printed wiring boards are commonly used, because they can be mounted relatively easily on the rear surfaces of casings such as instrument casings even if such rear surfaces are uneven in configuration, and also because they are lighter in weight than printed wiring boards of the rigid type and have excellent characteristics in terms of energy saving.
Such flexible printed wiring boards are, however, disadvantageous n that, since copper foils forming the electrical circuits thereof are arranged in a plurality of rows and occupy considerable width or space, in case casings such as instrument casings are manufactured with the minimum allowable dimensions, a portion of such a printed wiring board protrudes sidewise from the rear surface of the instrument casing and tends to contact other component part(s), thus causing a risk of damage of the component part(s) by the protruding portion and disconnection of the wirings.
As a prior art arrangement for solving the above-mentioned problem, there are heretofore known mounting structures for flexible printed wiring boards as shown in FIGS. 4, 5, 6 and 7.
Stating more specifically, a prior art embodiment shown in FIGS. 4 and 5 is arranged such that a groove-shaped accommodating portion 2 is defined by holding ribs 3 formed integrally with or separately from rear portion of an instrument board 1, and the protruding portion 4' of a flexible printed wiring board 4 is bent and inserted into the accommodating portion 2 thereby restraining the protruding portion 4' by the holding ribs 3 and preventing it from springing out.
Further, another prior art embodiment as shown in FIGS. 6 and 7 is arranged such that the protruding portion 4' of the flexible printed wiring board 4 is bent along side wall 1' of the instrument casing 1 so as to engage the protruding portion 4' with the side wall 1' thereby preventing the protrusion 4' from contacting other component part or parts.
However, in the case of the above-mentioned prior art embodiment shown in FIGS. 4 and 5, in case the length of the protruding portion of the flexible printed wiring board is long it can be fixedly secured and restrained, whilst in case the length of the protruding portion is short there is a risk of the protruding portion getting out of place simply from within the accommodating portion by the resiliency or the restoring force of the flexible printed wiring board.
Whilst, in the case of the above-mentioned prior art embodiment shown in FIGS. 6 and 7, in case there is an obstacle such as a built-in panel in the vicinity of an instrument casing, this securing mode cannot be used in practice, and also it is less reliable in fixedly securing the flexible printed wiring board.
The subject of the present invention is, therefore, to overcome the above-mentioned problem associated with the prior art mounting structure for flexible printed wiring boards.